Signal processing apparatus and method, network device and computer readable storage medium

ABSTRACT

Embodiments of the present disclosure provide a signal processing apparatus and method, a network device and a computer readable storage medium. The apparatus comprises: a receiving unit configured to receive a signal from a remote radio frequency unit (RRH), the RRH being independent from the signal processing apparatus; a processing unit configured to perform signal enhancement on the signal; and a transmitting unit configured to transmit the enhanced signal to a baseband unit (BBU). According to the present disclosure, it is possible to implement a fronthaul or anyhaul solution with a high reliability, and meanwhile save the RF transmission power of the terminal device and reduce the operation costs of the operators.

FIELD

Embodiments of the present disclosure relate to the field of wirelesscommunications, and more specifically to a signal processing apparatusand method, a network device and a computer readable storage medium.

BACKGROUND

As the 5^(th) generation mobile communication (5G) era comes, a solutionof wireless access and fiber based fronthaul or anyhaul attractsattention. Reliability of signals in the fronthaul or anyhaul is a keyrequirement to support a centralized processing based radio accessnetwork (C-RAN) architecture or a future edge-node based networkinfrastructure. To ensure the signal reliability from the respect of aphysical layer, radio frequency (RF) transmitting power is needed to beabove a certain threshold to meet a requirement for a signal-noise ratio(SNR). However, power saving is also critical for terminal devices thatare connected to the Internet, especially when Internet of Things(IOT)/Internet of Everything (JOE) is involved in the future.

SUMMARY

On the whole, embodiments of the present disclosure provide a signalprocessing apparatus and method and a network device.

In an aspect of the present disclosure, there is provided a signalprocessing apparatus. The apparatus comprises: a receiving unitconfigured to receive a signal from a remote radio frequency unit (RRH),the RRH being independent from the signal processing apparatus; aprocessing unit configured to perform signal enhancement on the signal;and a transmitting unit configured to transmit the enhanced signal to abaseband unit (BBU).

In another aspect of the present disclosure, there is provided a signalprocessing method. The method comprises: receiving a signal from an RRH;performing signal enhancement on the signal; and transmitting theenhanced signal to a BBU.

In a further aspect of the present disclosure, there is provided anetwork device. The network device comprises the above-mentioned signalprocessing apparatus.

In a further aspect of the present disclosure, there is provided acomputer readable storage medium. The computer readable storage mediumhas machine executable instructions stored thereon which, when executed,cause a machine to implement the above-mentioned signal processingmethod.

According to solutions of embodiments of the present disclosure, it ispossible to provide an improved physical layer transmission mechanism,thereby implementing a fronthaul or anyhaul solution with a highreliability, and meanwhile saving RF transmission power of a terminaldevice and reducing operation costs of an operator.

It will be appreciated that the Summary part does not intend to indicateessential or important features of embodiments of the present disclosureor to limit the scope of the present disclosure. Other features of thepresent disclosure will be made apparent by the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the following detailed description with reference to theaccompanying drawings, the above and other features, advantages andaspects of example embodiments of the present disclosure will becomemore apparent. In the drawings, identical or similar reference numbersrepresent the same or similar elements, in which:

FIG. 1 illustrates a schematic diagram of a communication scenario inwhich an embodiment of the present disclosure may be implemented;

FIG. 2 illustrates a schematic diagram of an example base stationarchitecture according to an embodiment of the present disclosure;

FIG. 3 illustrates a structural block diagram of a signal processingapparatus according to an embodiment of the present disclosure;

FIG. 4 illustrates a structural block diagram of a processing unit in asignal processing apparatus according to an embodiment of the presentdisclosure;

FIG. 5 illustrates a structural block diagram of a noise-spectrumshaping module in a processing unit according to an embodiment of thepresent disclosure;

FIG. 6 illustrates a flow chart of a signal processing method accordingto an embodiment of the present disclosure;

FIG. 7 illustrates a flow chart of a method for signal enhancementaccording to an embodiment of the present disclosure; and

FIG. 8 illustrates a simplified block diagram of a device adapted toimplement embodiments of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described with referenceto the drawings in detail. Though some embodiments of the presentdisclosure are shown in the drawings, it should be appreciated that thepresent disclosure can be implemented in various manners and should notbe interpreted as limited to the implementations described herein.Conversely, these implementations are provided for thorough and completeunderstanding of the present disclosure. It is to be understood that thedrawings and implementations are only for the purpose of example, ratherthan to limit the scope of protection of the present disclosure.

The term “network device” or “base station” used herein may represent anode B (NodeB or NB), an evolved node B (eNodeB or eNB), a repeater, ora low power node such as a femto station and a pico station and thelike. In the context of the present disclosure, for ease of discussion,terms “network device” and “base station” may be used interchangeably,and an eNB is mainly used as an example of a base station.

The term “terminal device” used herein refers to any terminal device oruser equipment (UE) that can perform wireless communication with basestations or with each other. As an example, the terminal device mayinclude a sensor, a detector, a mobile terminal (MT), a subscriberstation (SS), a portable subscriber station (PSS), a mobile station(MS), or an access terminal (AT) having a communication function and theabove vehicle-mounted devices. In the context of the present disclosure,for ease of discussion, terms “terminal device” and “user equipment” maybe used interchangeably, and UE is mainly used as an example of aterminal device.

As used herein, the term “include” and its variants are to be read asopen-ended terms that mean “include, but is not limited to.” The term“based on” is to be read as “based at least in part on.” The term “oneexample embodiment” is to be read as “at least one example embodiment,”and the term “another embodiment” is to be read as “at least one anotherembodiment.” Relevant definition for other terms will be given in thefollowing depiction.

FIG. 1 illustrates a schematic diagram of a communication scenario 100in which an embodiment of the present disclosure may be implemented. Tofacilitate discussion, an eNB is taken as an example of a base stationbelow, and UE is taken as an example of a terminal device. However, itshould be appreciated that this is only intended to facilitateillustration of ideas of embodiments of the present disclosure and notintended to limit the application scenarios and scope of the presentdisclosure in any manner.

As known in the art, a distributed base station architecture (as shownin a dotted-line block) including an RRH (e.g., RRH 110) and a BBU(e.g., BBU 120) is usually employed currently. The RRH 110 may be usedto perform RF processing for a signal from the terminal device 130, andthe BBU 120 may be used to perform baseband processing for the signal.Usually, one BBU may support one or more RRHs. In the case of one RRH,the RRH and BBU are connected via optical fibers and communicated via acommon public radio interface (CPRI), which is called fronthaul, asshown in FIG. 1. In the case of the plurality of RRHs, the plurality ofRRHs are gathered by a hub and then connected to respective BBUs viaoptical fibers, and communicated via Ethernet-based Common Public RadioInterface (eCPRI) protocol, which is called anyhaul or midhaul, notshown herein.

As mentioned above, there is a conflict between power saving and signalreliability in a terminal device. For example, an RF signal from theterminal device 130 is reduced to a smaller amplitude but modulatedusing a high-order Quadrature Amplitude Modulation (QAM) (e.g., 64QAM).However, conventionally, the RRH 110 is not sufficient to quantize aweak RF signal including a high-order QAM at a low RF transmission power(e.g., in a level of −150 dBm). Without any compensation, the BBU 120would fail to detect and restore the RF signal.

In the already-proposed solution, it is possible to replace a 16-bitanalog-to-digital converter in the RRH with a 20-bit analog-to-digitalconverter, or use a better low noise pre-amplifier in the RRH, or use alarge oversampling rate in RRH to oversample the weak RF signal, toensure the signal reliability. However, the implementation of thesesolutions requires a replacement of the conventional RRH, which consumesa lot of manpower and material resources.

In view of this, the present inventor proposes an improved solutionwhich can achieve an improvement of the signal reliability while keepingthe conventional RRH unchanged. Detailed description is presented belowwith reference to FIG. 2. FIG. 2 illustrates a schematic diagram of anexample base station architecture 200 according to an embodiment of thepresent disclosure.

According to the idea of the embodiment of the present disclosure, it ispossible to add a signal processing apparatus 210 between the RRH 110and the BBU 120 to achieve the signal enhancement function. This signalprocessing apparatus 210 is independent from the RRH 110. Specifically,it is possible to, through the signal processing apparatus 210, performsignal enhancement for the weak RF signal from the RRH 110, and thensend it to the BBU 120, thereby ensuring the signal reliability withoutchanging the conventional RRH. In this way, it is possible to permit alower transmission power and an enhanced RF throughput of a terminaldevice, and reduce operation costs of an operator.

According to an embodiment of the present disclosure, the signalprocessing apparatus 210 may be a pluggable member, and may be connectedbetween the RRH 110 and the BBU 120 in any proper manner. It should beappreciated that although the signal processing apparatus 210 in FIG. 2is shown as a member independent from the RRH 110 and the BBU 120, thesignal processing apparatus 210 may be arranged on the side of the RRH110, or on the side of the BBU 120.

In addition, it should be appreciated that the embodiment of the presentdisclosure only involves the processing of uplink data from a terminaldevice to a base station. Furthermore, the idea of the embodiments ofthe present disclosure provides a physical layer transmission mechanismhaving transparency with respect to different protocols such asfronthaul or anyhaul, and thus has a very good compatibility with thecurrently-used CPRI or eCPRI protocol.

Although one RRH 110 is shown in FIG. 2 here, the idea of the embodimentof the present disclosure may be applied for a plurality of RRHs 110. Inthis case, the signals from the plurality of RRHs 110 may be gathered bya hub, then the gathered signals are processed by the signal processingapparatus 210, and then the processed signals are transmitted to the BBU120. Although only one BBU 120 is shown in FIG. 2, it should beappreciated that the idea of the embodiment of the present disclosuremay also be applied for the case of a BBU pool including a plurality ofBBUs.

According to the embodiment of the present disclosure, the signalprocessing apparatus 210 may be implemented in any suitable manner solong as the signal enhancement function is implemented. An exampleimplementation of the signal processing apparatus 210 is described withreference to FIG. 3.

FIG. 3 illustrates a structural block diagram 300 of a signal processingapparatus according to an embodiment of the present disclosure. Forexample, the signal processing apparatus 210 may include a receivingunit 310, a processing unit 320 and a transmitting unit 330. Thereceiving unit 310 is configured to receive a signal from an RRH (e.g.,the RRH 110), the processing unit 320 is configured to perform signalenhancement for the signal, and the transmitting unit 330 is configuredto transmit the signal which has undergone the signal enhancement to aBBU (e.g., the BBU 120).

It should be appreciated that although the receiving unit, processingunit and transmitting unit are respectively shown as an independentelement in FIG. 3, in fact they may be implemented by more or lesselements. For example, the receiving unit and transmitting unit may beimplemented by a single transceiver. For example, the processing unitmay be implemented by one or more processors or controllers. This is byno means limited by the present disclosure.

Reference is made below to FIG. 4 to describe an example implementationof the processing unit 320. FIG. 4 illustrates a structural blockdiagram 400 of a processing unit in a signal processing apparatusaccording to an embodiment of the present disclosure. For example, theprocessing unit 320 may comprise a symbol reconstruction module 410, aresampling module 420, a noise-spectrum shaping module 430 and adown-sampling module 440.

In the embodiment of the present disclosure, the symbol reconstructionmodule 410 is configured to convert a bit stream of the signal from theRRH into a symbol stream. According to the embodiment of the presentdisclosure, for example, according to an analog-to-digital converter(ADC) resolution in the RRH, a 0-1 bit stream of the signal from the RRHmay be converted into a corresponding symbol stream. In fact, regardingthe coming RF signal having a very small amplitude, the ADC in the RRHcannot capture and restore details of the RF signal in the resolution,and a noise level therein is relatively higher. Therefore, it isnecessary to compensate for this. Its detailed description is madebelow.

In the embodiment of the present disclosure, the resampling module 420is configured to resample the symbol stream. According to the embodimentof the present disclosure, the resampling of the low-resolution symbolstream may be implemented by performing interpolation on the symbolstream and performing convolution on the interpolated signal. Forexample, in an embodiment, it is possible to perform the interpolationon the symbol stream by interpolating several points between two symbolsat a predetermined sampling rate (e.g., m). In an embodiment, it ispossible to perform the convolution on each symbol in the symbol streamby means of a kernel function.

It should be appreciated that the present disclosure is not limited tothe above examples of the interpolation and convolution, but theresampling can be implemented by any suitable interpolation andconvolution processing. In addition, the interpolation and convolutionmay be reconfigured via software according to each specific terminaldevice such as an IoT/IoE terminal device, so the method according tothe embodiment of the present disclosure exhibits higher flexibility andcontrollability.

In the embodiment of the present disclosure, the noise-spectrum shapingmodule 430 is configured to noise-spectrum shaping the resampled symbolstream. According to the embodiment of the present disclosure, thenoise-spectrum shaping is intended to implement redistribution of anoise-spectrum and filter out of out-of-band noise, thereby achievingthe signal enhancement. It should be appreciated that any suitablenoise-spectrum shaper or noise-spectrum shaping circuit may be employedto implement the noise-spectrum shaping. Reference is made below to FIG.5 to describe an example implementation of the noise-spectrum shapingmodule 430.

FIG. 5 illustrates an example structural block diagram 500 of anoise-spectrum shaping module in a processing unit according to anembodiment of the present disclosure. As shown in FIG. 5, the module maycomprise a feedback loop 510 and a filter 520. The feedback loop 510 maybe configured to perform noise-spectrum redistribution on the resampledsymbol stream, whereby the noise-spectrum is migrated out of the band(e.g., higher frequency band). The filter 520 may be configured toperform filtering on the noise-spectrum redistributed symbol stream,thereby filtering away the out-of-band noise so that the signal has asmaller noise and is enhanced.

According to the embodiment of the present disclosure, the feedback loop510 may comprise an adder 511, an integrator 512, a comparator 513 and aD flip-flop 514. One input of the adder 511 receives the resampledsymbol stream, and another input receives a negative output from the Dflip-flop 514. Input of the integrator 512 receives output from theadder 511. One input of the comparator 513 receives output from theintegrator 512, and another input is connected with a referencepotential (e.g., grounded). Input of the D flip-flop 514 receives outputfrom the comparator 513, and its positive output is connected to thefilter 520. It should be appreciated that the feedback loop is notlimited to the shown configuration, but can be implemented by using anysuitable configuration.

According to the embodiment of the present disclosure, the filter 520may be a low-pass filter. It may be appreciated that the filter 520 mayemploy other suitable types of filters according to needs.

The noise-spectrum shaping module stated above with reference to FIG. 6is a first-order noise-spectrum shaper. It should be appreciated that itis possible to select and use higher-order noise-spectrum shaperaccording to needs and acceptable complexity. The higher-ordernoise-spectrum shaper will not be listed one by one here.

The example implementation of the noise-spectrum shaping module isdescribed above. Now returning to FIG. 4, in the embodiment of thepresent disclosure, the down-sampling module 440 is configured toperform down-sampling processing on the noise-spectrum shaped symbolstream. The original symbol stream is reconfigured according to thesampling rate (e.g., m) in the resampling module 420. The originalsymbol stream has the same length, but the noise is substantiallyreduced.

In this way, according to the solution of the embodiment of the presentdisclosure, the noise moves to higher frequency bands through resamplingand noise-spectrum shaping and filtering, so that the in-band noisesubstantially reduces and a clear low-frequency band signal is obtained.The low-frequency band signal is transmitted to the BBU so that it isdetected and restored intact. Therefore, signal reliability is ensured.

Correspondingly, the embodiment of the present disclosure provides asignal processing method. Detailed depictions will be presented withreference to FIG. 6 and FIG. 7. FIG. 6 illustrates a flow chart of asignal processing method 600 according to an embodiment of the presentdisclosure. The method 600 for example may be implemented at the signalprocessing apparatus 210 in FIG. 2.

As shown in FIG. 6, at 610, the signal processing apparatus 210 mayreceive the signal from the RRH 110. In the case of a low power terminaldevice involving IoT/IoE, the signal is a weak RF signal with a lowresolution.

At 620, the signal processing apparatus 210 may perform signalenhancement for the received signal. According to the embodiment of thepresent disclosure, signal enhancement may be implemented throughresampling and noise-spectrum shaping and filtering. An exampleimplementation process is described below with reference to FIG. 7.

FIG. 7 illustrates a flow chart of a method 700 for signal enhancementaccording to an embodiment of the present disclosure. As shown in FIG.7, at 710, the bit stream of the signal may be converted into a symbolstream to implement symbol reconstruction for subsequent processing. Theprocessing in this step is similar to the operation described above inconjunction with the symbol reconstruction module 410, and will not bedetailed any more here.

At 720, perform resampling processing for the symbol stream. Accordingto the embodiment of the present disclosure, for example it is possibleto implement resampling by performing interpolation and convolution oneach symbol in the symbol stream. The processing in this step is similarto the operation described above in conjunction with the resamplingmodule 420, and will not be detailed any more here.

At 730, it is possible to perform noise-spectrum shaping processing forthe symbol stream which has undergone the resampling processing.According to the embodiment of the present disclosure, it is possible toperform noise-spectrum redistribution on the resampled symbol stream,and perform filtering on the noise-spectrum redistributed symbol stream.This may be implemented by any suitable noise-spectrum shaper ornoise-spectrum shaping circuit. According to the embodiment of thepresent disclosure, it is possible to perform noise-spectrumredistribution on the resampled symbol stream via the feedback loop. Forexample, reference is made to the circuit described with reference toFIG. 5. According to the present embodiment, it is possible to,respectively via first input and second input of the adder 511 of thefeedback loop 510, receive the resampled symbol stream and negativeoutput from the D flip-flop 514; provide output from the adder 511 tothe integrator 512; use the comparator 513 to compare output from theintegrator and the reference potential; and provide a comparison resultof the comparator 513 to the D flip-flop 514. The positive output of theD flip-flop 514 is connected to the filter 520 and used to performfiltering on the noise-spectrum redistributed symbol stream. Theprocessing in this step is similar to the operation described above inconjunction with the noise-spectrum shaping module 430, and will not bedetailed any more here.

At 740, it is possible to perform down-sampling processing on the symbolstream which has undergone noise-spectrum shaping processing, therebyimplementing regeneration of the symbol. As compared with the originalsymbol at step 710, the regenerated symbol has the same length, butnoise is substantially reduced.

Returning to FIG. 6, at 630, the signal processing apparatus 210 sendsthe signal after the signal enhancement (namely the regenerated symbolstream in step 740) to the BBU 120. Therefore, the BBU 120 may detectand restore a high-order QAM signal having a proper intensity.

So far, the signal processing method is described, it corresponds to theoperations of the signal processing apparatus described above withreference to FIG. 2 through FIG. 5, and other processing details may befound from the above depictions with reference to FIG. 2 through FIG. 5,and will not be detailed any more here.

According to example embodiments of the present disclosure, it ispossible to substantially reduce the transmission power of the terminaldevice and enable the service life of the battery of the terminal deviceto increase. In addition, it is applicable to the high-order QAM in awireless system. Furthermore, wireless makes changes to wirelessprocessing of wireless components in the current network architecture,and is adapted for currently-used various fronthaul or anyhaul protocolssuch as CPRI or eCPRI.

FIG. 8 illustrates a simplified block diagram of a device 800 adapted toimplement embodiments of the present disclosure. The device 800 may beused to implement the signal processing apparatus according toembodiments of the present disclosure (e.g., the signal processingapparatus 210 of FIG. 2).

As shown in the figure, the device 800 comprises one or more processors810, one or more memories 820 coupled to the processor 810, and one ormore transmitters and/or receivers (TX/RX) 840 coupled to the processor(s) 810.

The processor 810 may be in any suitable type adapted for localtechnical environment, and may include but not limited to one or more ofa general-purse computer, a dedicated computer, a microcomputer, adigital signal processor (DSP) and a process-based multi-core processorarchitecture. The device 800 may also include a plurality of processors,for example a dedicated integrated circuit chip temporally following aclock synchronous with a main processor.

The memory 820 may be in any suitable type adapted for local technicalenvironment, and may be implemented using any suitable data storagetechnology. Non-restrictive examples of the memory are for example anon-transient computer-readable storage medium, a semiconductor-basedstorage device, a magnetic storage device and system, an optical storagedevice and system, a fixed memory and a removable memory.

The memory 820 stores at least part of the program 830. TX/RX 840 isused for bidirectional communication. The TX/RX 840 has at least oneantenna to promote communication. However, in practice the device mayhave several antennas. The communication interface may represent anyinterface needed in communicating with other network elements.

The program 830 may comprise a program instruction. The programinstruction, when executed by the associated processor 810, enables thedevice 800 to operate according to the embodiment of the presentdisclosure, as stated with reference to FIG. 3 through FIG. 7. That isto say, embodiments of the present disclosure may be implemented bycomputer software executed by the processor 810 of the device 800, orimplemented by hardware, or implemented by software and hardware incombination.

Generally, various exemplary embodiments of the present disclosure maybe implemented in hardware or application-specific circuit, software,logic, or in any combination thereof. Some aspects may be implemented inhardware, while the other aspects may be implemented in firmware orsoftware executed by a controller, a microprocessor or other computingdevice. When various aspects of the present invention are illustrated ordescribed into block diagrams, flowcharts, or other graphicalrepresentations, it would be appreciated that the block diagrams,apparatus, system, technique or method described here may beimplemented, as non-restrictive examples, in hardware, software,firmware, dedicated circuit or logic, common software or controller orother computing device, or some combinations thereof. Examples forimplementing hardware devices of embodiments of the present disclosurecomprise but not limited to: a field-programmable gate arrays (FPGA),Application Specific Integrated Circuit (ASIC), Application SpecificStandard Parts (ASSP), System on Chip (SOC), Complex Programmable LogicDevice (CPLD) and the like.

As an example, the implementations of the subject matter disclosedherein can be described in a context of machine-executable instructionswhich are included, for instance, in the program module executed in thedevice on a target real or virtual processer. Generally, a programmodule includes routine, program, bank, object, class, component anddata structure, etc. and performs a particular task or implements aparticular abstract data structure. In the implementations, thefunctions of the program modules can be combined or divided among thedescribed program modules. The machine executable instructions for theprogram module can be executed in a local or distributed device. In thedistributed device, the program module can be located between the localand remote storage mediums.

The computer program code for implementing the method of the presentdisclosure may be complied with one or more programming languages. Thesecomputer program codes may be provided to a general-purpose computer, adedicated computer or a processor of other programmable data processingapparatus, such that when the program codes are executed by the computeror other programmable data processing apparatus, thefunctions/operations prescribed in the flowchart and/or block diagramare caused to be implemented. The program code may be executedcompletely on a computer, partially on a computer, partially on acomputer as an independent software packet and partially on a remotecomputer, or completely on a remote computer or server.

In the context of the present disclosure, the machine-readable mediummay be any tangible medium including or storing a program for or aboutan instruction executing system, apparatus or device. Themachine-readable medium may be a machine-readable signal medium ormachine-readable storage medium. The machine-readable medium mayinclude, but not limited to, electronic, magnetic, optical,electro-magnetic, infrared, or semiconductor system, apparatus ordevice, or any appropriate combination thereof. More detailed examplesof the machine-readable storage medium includes, an electricalconnection having one or more wires, a portable computer magnetic disk,hard drive, random-access memory (RAM), read-only memory (ROM), erasableprogrammable read-only memory (EPROM or flash memory), optical storagedevice, magnetic storage device, or any appropriate combination thereof.

Besides, although the operations are depicted in a particular sequence,it should not be understood that such operations are completed in aparticular sequence as shown or in a successive sequence, or all shownoperations are executed so as to achieve a desired result. In somecases, multi-task or parallel-processing would be advantageous.Likewise, although the above discussion includes some specificimplementation details, they should not be explained as limiting thescope of any invention or claims, but should be explained as adescription for a particular implementation of a particular invention.In the present invention, some features described in the context ofseparate implementations may also be integrated into a singleimplementation. On the contrary, various features described in thecontext of a single implementation may also be separately implemented ina plurality of implementations or in any suitable sub-group.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter specified in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. A signal processing apparatus, comprising: a receiving unitconfigured to receive a signal from a remote radio frequency unit (RRH),the RRH being independent from the signal processing apparatus; aprocessing unit configured to perform signal enhancement on the signal;and a transmitting unit configured to transmit the enhanced signal to abaseband unit (BBU).
 2. The apparatus according to claim 1, wherein theprocessing unit comprises: a symbol reconstruction module configured toconvert a bit stream of the signal into a symbol stream; a resamplingmodule configured to resample the symbol stream; a noise-spectrumshaping module configured to noise-spectrum shape the resampled symbolstream; and a down-sampling module configured to down-sample thenoise-spectrum shaped symbol stream.
 3. The apparatus according to claim2, wherein the resampling module comprises: an interpolation moduleconfigured to perform interpolation on the symbol stream; and aconvolution module configured to perform convolution on the interpolatedsymbol stream.
 4. The apparatus according to claim 2, wherein thenoise-spectrum shaping module comprises: a feedback loop configured toperform noise-spectrum redistribution on the resampled symbol stream;and a filter configured to filter the noise-spectrum redistributedsymbol stream.
 5. The apparatus according to claim 4, wherein thefeedback loop comprises: an adder having a first input to receive theresampled symbol stream and a second input to receive a negative outputfrom a D flip-flop; an integrator having an input to receive an outputfrom the adder; a comparator having a first input to receive an outputfrom the integrator and a second input connected to a referencepotential; and the D flip-flop having an input to receive an output fromthe comparator and a positive output connected to the filter.
 6. Asignal processing method, comprising: receiving a signal from a remoteradio frequency unit (RRH); performing signal enhancement on the signal;and transmitting the enhanced signal to a baseband unit (BBU).
 7. Themethod according to claim 6, wherein performing signal enhancement onthe signal comprises: converting a bit stream of the signal into asymbol stream; resampling the symbol stream; noise-spectrum shaping theresampled symbol stream; and down-sampling the noise-spectrum shapedsymbol stream.
 8. The method according to claim 7, wherein resamplingthe symbol stream comprises: performing interpolation on the symbolstream; and performing convolution on the interpolated symbol stream. 9.The method according to claim 7, wherein noise-spectrum shaping theresampled symbol stream comprises: performing noise-spectrumredistribution on the resampled symbol stream; and filtering thenoise-spectrum redistributed symbol stream.
 10. The method according toclaim 9, wherein performing noise-spectrum redistribution on theresampled symbol stream comprises: performing noise-spectrumredistribution on the resampled symbol stream via a feedback loop,comprising: receiving a negative output from a D flip-flop and theresampled symbol stream, respectively, via a first input and a secondinput of an adder in the feedback loop; providing an output from theadder to an integrator; comparing an output from the integrator with areference potential using a comparator; and providing a comparisonresult of the comparator to the D flip-flop, a positive output of the Dflip-flop being connected to a filter for performing the filtering. 11.A network device, comprising the apparatus according to claim
 1. 12. Acomputer readable storage medium having machine executable instructionsstored thereon which, when executed, cause a machine to implement themethod according to claim 6.